Printable etching media for silicon dioxide and silicon nitride layers

ABSTRACT

The present invention relates to a novel printable etching medium having non-Newtonian flow behaviour for the etching of surfaces in the production of solar cells, and to the use thereof. The present invention furthermore also relates to etching and doping media which are suitable both for the etching of inorganic layers and also for the doping of underlying layers. In particular, they are corresponding particle-containing compositions by means of which extremely fine structures can be etched very selectively without damaging or attacking adjacent areas.

The present invention relates to novel compositions in the form ofprintable etching media having non-Newtonian flow behaviour for theetching of surfaces in applications for the production of solar cells,and to the use thereof. The present invention furthermore also relatesto compositions in the form of etching and doping media which aresuitable both for the etching of extremely fine lines or structures ininorganic layers and also for the doping of underlying layers. Inparticular, they are corresponding particle-containing compositions bymeans of which extremely fine lines and structures can be etched veryselectively without damaging or attacking adjacent areas.

PRIOR ART AND OBJECT OF THE INVENTION

During the process for the production of solar cells, it is necessary,inter alia, to structure oxide layers on a support material. Acrystalline silicon solar cell usually consists of a p-conductingsubstrate, into which a homogeneously thick layer of an n-conductingsubstance, for example phosphorus, is diffused on the front. Ametallically conducting contact is applied to the front and back of thewafer in order to conduct away the current produced on incidence oflight. With a view to an inexpensive production method which is suitablefor mass production, the contact is usually produced by screen printing.

Besides the oxide layers that have to be structured during solar cellproduction, silicon nitride layers also have to be etched. For etchingcorresponding nitride layers, the methods used have to be modified andthe etching pastes adapted in a suitable manner.

The surfaces of crystalline silicon solar cells are coated with thininorganic layers during the production process, and optionally alsoafter the end thereof. These layers have thicknesses in the range from20 to 200 nm, in most cases in the range from 50 to 150 nm.

During the process for the production of crystalline silicon solarcells, it is therefore advantageous in a number of process steps to etchfine lines into these inorganic layers of the solar cell.

These openings in the surface of the solar cell can be used, forexample, for the production of a so-called selective emitter, also knownas 2-stage emitter. To this end, a high degree of n-doping, preferablyby means of phosphorus diffusing in, is produced in a subsequentdiffusion step in the partial openings of a diffusion barrier located onthe silicon.

In the present description, the term inorganic surfaces is taken to meanoxidic and nitride-containing compounds of silicon, in particularsilicon oxide and silicon nitride surfaces. The mode of action of suchdiffusion barriers is known to the person skilled in the art and isdescribed in the literature [A. Goetzberger; B. Voβ; J. Knobloch,Sonnenenergie: Photovoltaik [Solar Energy: Photovoltaics], TeubnerStudienbücher Stuttgart 1997, pp 40; 107]. These diffusion barriers canbe produced in a variety of ways:

Very dense silicon dioxide layers are obtained, for example, by heattreatment of silicon in an oxygen-containing atmosphere at temperaturesin the region of 900° C. (thermal oxide).

Also known to the person skilled in the art is the deposition of silicondioxide by CVD processes. Depending on the way the reaction is carriedout, a distinction is made here between, inter alia, the followingprocesses:

-   -   APCVD (atmospheric pressure CVD)    -   PE-CVD (plasma enhanced CVD)    -   LP-CVD (low pressure CVD)

A common feature of these processes is that the desired inorganiccompound is obtained from the gas phase of a volatile precursor, forexample silane (SiH₄) or TEOS (tetraethyl orthosilicate) in the case ofsilicon dioxide, by deposition of the precursor on the target substratewith decomposition.

Silicon dioxide layers which form a diffusion barrier can also beobtained by means of wet-chemical coating with a liquid or dissolvedsolid precursor in a solvent or solvent mixture. These liquid systemsare usually applied to the substrate to be coated by spin coating. Thesesystems are known to the person skilled in the art as spin-on-glass(SOG).

In many cases, the SiO₂ layer applied also remains asreflection-reducing passivation layer. This is particularly frequentlythe case for thermally grown SiO₂.

Silicon nitride layers are used less as diffusion barriers in the art ofcrystalline solar cells, although they are in principle likewisesuitable for this purpose. Silicon nitride layers are mainly used aspassivation and anti-reflection layers.

It is also advantageous in the production of crystalline silicon solarcells to be able to produce openings in a targeted manner in the siliconnitride layers. An example which may be mentioned here is theapplication of electrically conductive pastes. These metal pastes areusually “fired through” the silicon nitride layer at temperatures in theregion of 600° C., facilitating an electrical contact to the emitterlayer. Due to the high temperatures, polymer-based (epoxy or phenolicresin) metallisation pastes cannot be used. Crystal defects and metalliccontamination in the underlying silicon also arise in the “fire-throughprocess”. Due to the system, the passivation layer is additionallycompletely destroyed by the overlying printed-on metal paste. A partial,narrower opening of the silicon nitride layer for electrical contactingwould be more advantageous, with retention of the passivation layer inthe edge regions, which are covered by the overlying metallisationlayer.

Besides the pure diffusion barriers consisting of silicon dioxide orsilicon nitride, it is also possible to use thin glass layers in theproduction of crystalline silicon solar cells.

Definition of Glass:

Glass is taken to mean per se a homogeneous material, for examplequartz, window glass, borosilicate glass, and also thin layers of thesematerials produced on other substrates (for example ceramics, metalsheets, silicon wafers) by various processes known to the person skilledin the art (CVD, PVD, spin-on, thermal oxidation, inter alia).

The term glasses below is taken to mean silicon oxide- and siliconnitride-containing materials which are in the solid amorphous physicalstate without crystallisation of the glass components and which have ahigh degree of structural disorder in the microstructure owing to thelack of long-range order.

Besides pure SiO₂ glass (quartz), all glasses (for example dopedglasses, such as borosilicate, phosphosilicate and borophosphosilicateglasses, coloured, milk and crystal glasses, optical glasses) whichcomprise SiO₂ and other components, in particular elements such as, forexample, calcium, sodium, aluminium, lead, lithium, magnesium, barium,potassium, boron, beryllium, phosphorus, gallium, arsenic, antimony,lanthanum, zinc, thorium, copper, chromium, manganese, iron, cobalt,nickel, molybdenum, vanadium, titanium, gold, platinum, palladium,silver, cerium, caesium, niobium, tantalum, zirconium, neodymium,praseodymium, which occur in the glasses in the form of oxides,carbonates, nitrates, phosphates, sulfates and/or halides or function asdoping elements in the glasses, are also encompassed. Doped glasses are,for example, borosilicate, phosphosilicate, borophosphosilicate,coloured, milk and crystal glasses and optical glasses. The siliconnitride may likewise comprise other elements, such as boron, aluminium,gallium, indium, phosphorus, arsenic or antimony.

Definition of silicon oxide- and silicon nitride-based systems: Siliconoxide-based systems are defined below as all crystalline systems whichdo not fall under the definition of amorphous SiO₂ glasses given aboveand are based on silicon dioxide; these can be, in particular, the saltsand esters of orthosilicic acid and condensation productsthereof—generally known as silicates by the person skilled in the art—aswell as quartz and glass-ceramics.

Furthermore, other silicon oxide- and silicon nitride-based systems, inparticular the salts and esters of orthosilicic acid and condensationproducts thereof, are encompassed. Besides pure SiO₂ (quartz, tridymite,cristobalite), all SiO₂-based systems built up from SiO₂ or “discrete”and/or linked [SiO₄] tetrahedra, such as, for example, mesosilicates,sorosilicates, cyclosilicates, inosilicates, phyllosilicates,tectosilicates, and comprising other components, in particularelements/components such as, for example, calcium, sodium, aluminium,lithium, magnesium, barium, potassium, beryllium, scandium, manganese,iron, titanium, zirconium, zinc, cerium, yttrium, oxygen, hydroxylgroups and halides, are also encompassed.

Silicon nitride-based systems are defined below as all crystalline andpartially crystalline (usually referred to as microcrystalline) systemswhich do not fall under the definition given above for the amorphoussilicon nitride glasses/layers. These include Si₃N₄ in its α-Si₃N₄ andβ-Si₃N₄ modifications and all crystalline and partially crystallineSiN_(x) and SiN_(x):H layers. Crystalline silicon nitride may compriseother elements, such as boron, aluminium, gallium, indium, phosphorus,arsenic and antimony.

Etching of Structures

The use of etchants, i.e. chemically aggressive compounds, results inthe dissolution of the material exposed to the etchant attack. In mostcases, the aim is completely to remove the layer to be etched. The endof the etching is reached by the encountering of a layer which issubstantially resistant to the etchant. In addition, there is theprocess known to the person skilled in the art of partial removal of alayer by etching to a target thickness which is usually defined.

Etching of structures on silicon oxide- and silicon nitride-basedglasses and other silicon oxide- and silicon nitride-based systems:

According to the current state of the art, any desired structures can beetched selectively in silicon oxide- and silicon nitride-based glassesand other silicon oxide- and silicon nitride-based systems or surfacesthereof and layers thereof of variable thickness directly bylaser-supported etching methods or, after masking, by wet-chemicalmethods ([1] D. J. Monk, D. S. Soane, R. T. Howe, Thin Solid Films 232(1993), 1; [2] J. Bühler, F.-P. Steiner, H. Baltes, J. Micromech.Microeng. 7 (1997), R1) or by dry-etching methods ([3] M. Köhler“Ätzverfahren für die Mikrotechnik” [Etching Methods forMicrotechnology], Wiley VCH 1983).

In the laser-supported etching methods, the laser beam scans the entireetching pattern on the glass dot by dot or line by line in the case ofvector-orienting systems, which, besides a high degree of precision,also requires considerable adjustment effort and time.

The wet-chemical and dry-etching methods include material-intensive,time-consuming and expensive process steps:

A. Masking of the Areas not to be Etched, for Example by:

-   -   photolithography: Production of a negative or positive of the        etching structure (depending on the resist), coating of the        substrate surface (for example by spin-coating with a liquid        photoresist), drying of the photoresist, exposure of the coated        substrate surface, development, rinsing, optionally drying

B. Etching of the Structures by:

-   -   dip methods (for example wet etching in wet-chemistry benches):        dipping of the substrates into the etching bath, etching        operation, repeated rinsing in H₂O cascade sinks, drying    -   spin-on or spray methods: the etching solution is applied to a        rotating substrate, the etching operation can be carried out        without/with input of energy (for example IR or UV irradiation),        this is followed by rinsing and drying    -   dry-etching methods, such as, for example, plasma etching, in        expensive vacuum units or etching with reactive gases in flow        reactors        C. Removal of the photoresist:

In a final process step, the photoresist covering the protecting areasof the substrate must be removed. This can be carried out by means ofsolvents, such as, for example, acetone, or dilute aqueous alkalinesolutions. The substrates are finally rinsed and dried.

Full-area etching of silicon oxide- and silicon nitride-based glassesand other silicon oxide- and silicon nitride-based systems:

In order to etch silicon oxide- and silicon nitride-based glasses andother silicon oxide- and silicon nitride-based systems and layers ofvariable thickness thereof over the entire area completely or only to acertain depth, use is predominantly made of wet-etching methods. Thesilicon oxide- and silicon nitride-based glasses and other siliconoxide- and silicon nitride-based systems and layers of variablethickness thereof are dipped into etching baths, which usually containthe toxic and highly caustic hydrofluoric acid and optionally additivesof other mineral acids.

The disadvantages of the etching methods described lie in thetime-consuming, material-intensive and expensive process steps which arein some cases complex in technological and safety terms and arefrequently carried out discontinuously.

International Application WO 01/83391 A describes etching media in theform of printable, homogeneous, particle-free etching pastes havingnon-Newtonian flow behaviour for the etching of inorganic, glass-likeamorphous or crystalline surfaces, in particular of glasses or ceramics,preferably SiO₂— or silicon nitride-based systems, and the use of theseetching media. In particular on printing of surfaces, use of theseparticle-free media gave rise to problems due to inadequate resilienceof the printed lines, dots or structures (inadequate structurefidelity), meaning that a significant broadening of the originallyprinted lines occurs (bleeding of the etching species on the substrate).

U.S. Pat. No. 5,688,366 A uses particle-containing etching pastes foretching a transparent conductive layer (for example ITO). The etchingpastes used are prepared from molten iron chloride containing water ofcrystallisation, glycerol and polymer particles. These compositions aresuitable for etching lines having a width of about 1 mm. Experimentshave shown that these etching pastes are not suitable for etching verythin lines having a width of less than 1 mm cleanly and without flaws,irrespective of whether polymer particles having a diameter of 0.01 μmor of 30 μm are employed for the preparation of the pastes.

OBJECTIVE

The object of the present invention is therefore to provide novel,inexpensive etching pastes for etching very uniform thin lines having awidth of less than 100 μm, in particular of less than 80 μm, andextremely fine structures on silicon dioxide and/or silicon nitridelayers which are located on silicon solar cells. A further object of thepresent invention is to provide novel etching media which can be removedfrom the treated surfaces after the etching, if necessary under theaction of heat, in a simple manner without leaving residues.

DESCRIPTION OF THE INVENTION

More recent experiments have now shown that, contrary to experience todate, the technical printing properties of etching pastes canadvantageously be improved if suitable, selected finely particulatepowders are added. The addition of inorganic, finely particulate powdershas proven particularly suitable. These can be incorporated into theetching media together with suitable polymer particles. In particular,inorganic powders can be incorporated together with polymer particleswhich form a network in the resultant pastes by physical interactionand/or chemical reaction with the other constituents of the medium, atthe same time resulting in an increase in the viscosity of thecomposition. Entirely unexpectedly, the added polymer particlescontribute to an improvement in the printability of the medium, whilethe added inorganic particles have an advantageous effect on thesubsequent cleaning step.

Accordingly, the present object is achieved through the use ofcorresponding powders in compositions for the etching of inorganic,glass-like or crystalline surfaces selected from the group of glassesbased on silicon oxide and glasses based on silicon nitride.

Given a suitable choice of the added particulate components, it may evenbe possible completely to omit the addition of a thickener, which isusually homogeneously distributed in known particle-free pastes.Contrary to all expectations and surprisingly for the person skilled inthe art, the compositions according to the invention in the form ofpastes can be printed to give extremely fine, uniform and homogeneouslines and structures.

The object of the present application is therefore also achieved by theprovision of a novel printable composition in the form of a paste forthe etching of inorganic, glass-like or crystalline surfaces selectedfrom the group of glasses based on silicon oxide and glasses based onsilicon nitride, which comprises inorganic, finely particulate powdersand optionally polymer powders consisting of a material selected fromthe group polystyrene, polyacrylate, polyamide, polyimide,polymethacrylate, melamine resin, urethane resin, benzoguanine resin,phenolic resin, silicone resin, fluorinated polymers (PTFE, PVDF, interalia) and micronised wax, in the presence of at least one etchingcomponent, solvents, thickeners, optionally at least one inorganicand/or organic acid, and optionally additives, such as antifoams,thixotropic agents, flow-control agents, deaerators, adhesion promoters,and which is active at temperatures in the range from 30 to 500° C. orcan optionally be activated by input of energy. Preferred groups ofparticles which are used in the etching compositions according to theinvention in the form of pastes are the subject-matter of Claims 2-11.Features of the compositions prepared using the finely particulatepowders are the subject-matter of Claims 12 to 26. The present inventionfurthermore relates to a process for the etching of inorganic,glass-like, crystalline surfaces in accordance with Claims 27 to 30.

DETAILED DESCRIPTION OF THE INVENTION

Experiments have shown that the use of finely particulate powders inetching compositions in the form of pastes enables both the behaviour ofthe pastes during the printing process and also the achievable etchingresult to be significantly improved. Surprisingly, it has been foundthat the addition of selected finely particulate powders mayconsiderably improve the edge sharpness of the etched lines orstructures, but also favourably influences the properties of thecompositions with respect to the stability of the printed lines orstructures.

The present invention thus relates, in particular, to the use of finelyparticulate inorganic and/or organic powders in compositions for theetching of inorganic, glass-like or crystalline surfaces selected fromthe group of glasses based on silicon oxide and glasses based on siliconnitride, in particular corresponding layers which are of importance inphotovoltaics.

The present invention thus also relates, in particular, to compositionsin the form of a printable etching paste for the etching and optionallyfor the doping of inorganic glass-like or crystalline layers selectedfrom the group of glasses based on silicon dioxide and glasses based onsilicon nitride, which are located on crystalline or amorphous siliconsurfaces, in which

-   a) at least one etching component,-   b) at least one solvent,-   c) at least one inorganic powder in the form of finely particulate    graphite and/or carbon black, and optionally finely particulate    organic powder in the form of finely particulate plastic powders    selected from the group of polystyrenes, polyacrylates, polyamides,    polyimides, polymethacrylates, melamine resin, urethane resin,    benzoguanine resin, phenolic resin, silicone resins, micronised    cellulose and fluorinated polymers (PTFE, PVDF),    -   and optionally micronised wax,    -   and optionally inorganic particles from the group aluminium        oxides, calcium fluoride, boron oxide, sodium chloride,-   d) at least one fluxing agent additive,-   e) optionally a homogeneously dissolved organic thickener,-   f) optionally at least one inorganic and/or organic acid, and    optionally-   g) additives, such as antifoams, thixotropic agents, flow-control    agents, deaerators, adhesion promoters,    are present.

In accordance with the invention, corresponding printable etching mediacomprise, in particular, at least one inorganic powder in the form offinely particulate graphite and/or carbon black and/or finelyparticulate organic powder in the form of finely particulate plasticpowders selected from the group

polystyrenes, polyacrylates, polyamides, polyimides, polymethacrylates,melamine resin, urethane resin, benzoguanine resin, phenolic resin,silicone resins, micronised cellulose, fluorinated polymers (PTFE, PVDF)and optionally micronised waxes,and optionally inorganic particles selected from the group aluminiumoxide, calcium fluoride, boron oxide, sodium chloride.

Particularly suitable in accordance with the invention are compositionswhich comprise an inorganic powder whose particles have a relativediameter of <5 μm.

Finely particulate organic powders present therein can have a relativeparticle diameter in the range from 10 nm to 50 μm. However, preferenceis given to the incorporation into the media of organic powders having arelative particle diameter in the range from 100 nm to 30 μm and veryparticularly preferably from 1 μm to 10 μm.

Depending on the desired area of application, the etching media maycomprise powders in an amount of 1 to 80% by weight, based on the totalamount. For the printing and etching of thin lines and fine structures,use can be made of etching media which comprise powders in an amount of10 to 50% by weight, in particular in an amount of 20 to 40% by weight,based on the total amount, where inorganic powder having a relativeparticle diameter of <5 μm is advantageously present therein in anamount of at least 0.5 to 5% by weight, based on the total amount of theetching medium.

The etching media according to the invention comprise at least oneetching component. It has been found in practice that suitable etchingmedia may comprise one or more etching components in an amount of 12 to30% by weight, based on the total amount. Good results are achieved withetching media in which the latter are present in an amount in the rangefrom 2 to 20% by weight. Particular preference is given to the use ofmedia in which the proportion of etching components is in the range from5 to 15% by weight, based on the total amount, since these compositionsresult in very selective etching results at the desired high etchingrates.

The particulate powders added to the compositions effect an increase inthe viscosity. This is associated with improved printing properties andthe possibility of printing and etching finer lines and structures.Since the compositions applied to the surfaces to be treated afterprinting during the etching process have a lower tendency to bleed, moreprecise lines can be etched. This is all the more surprising sinceearlier attempts to use particulate thickeners in the compositions gavequalitatively unsuitable etching results. The more recent experimentshave now shown that added finely particulate powders and the othercomponents must interact with one another in such a way that, afterintensive mixing of the individual components, a homogeneous mixture isformed which has a suitable viscosity which facilitates simple printingof the pastes, but no longer allows bleeding.

In order to adjust the viscosity and in order to achieve an advantageousprinting behaviour, additional thickeners may be incorporated into theetching media in an amount of 0.5-25% by weight, based on the totalamount. These can be one or more homogeneously dissolved thickeners fromthe group

cellulose/cellulose derivatives and/orstarch/starch derivatives and/orpolyvinylpyrrolidonepolymers based on acrylates or functionalised vinyl units.

Preference is given to the addition of thickeners in an amount of 3 to20% by weight, based on the total amount of the etching medium.

As is known from the literature, various etching media components whichhave an etching action are also suitable for the doping of semiconductorlayers. It has therefore proven advantageous for the printable etchingpaste compositions according to the invention to comprise one or moreforms of phosphoric acid, phosphoric acid salts or compounds which aredecomposed to the corresponding phosphoric acid on heating. Since dopingby the phosphoric acids can also occur at very high temperatures, thishas the advantage that etching and subsequent doping of the underlying,exposed layer can be carried out directly successively through the useof only one composition.

The present invention thus relates to a composition in the form of apaste which comprises at least one inorganic mineral acid selected fromthe group hydrochloric acid, phosphoric acid, sulfuric acid and nitricacid as etching component and/or optionally at least one organic acid,which may contain a straight-chain or branched alkyl radical having 1-10C atoms, selected from the group of the alkylcarboxylic acids, thehydroxycarboxylic acids and the dicarboxylic acids. Suitable organicacids are those selected from the group formic acid, acetic acid, lacticacid and oxalic acid.

In total, the proportion of the organic and/or inorganic acids in thecompositions according to the invention in the form of etching pastescan be in a concentration range from 0 to 80% by weight, based on thetotal amount of the medium. It has proven advantageous for the addedacids each to have a pK_(a) value of between 0 and 5.

Besides water, solvents which may be present in the etching mediumcomposition according to the invention are mono- or polyhydric alcohols,such as glycerol, 1,2-propanediol, 1,4-butanediol, 1,3-butanediol,1,5-pentanediol, 2-ethyl-1-hexenol, ethylene glycol, diethylene glycoland dipropylene glycol, and ethers thereof, such as ethylene glycolmonobutyl ether, triethylene glycol monomethyl ether, diethylene glycolmonobutyl ether and dipropylene glycol monomethyl ether, and esters,such as [2,2-butoxy(ethoxy)]ethyl acetate, esters of carbonic acid, suchas propylene carbonate, ketones, such as acetophenone,methyl-2-hexanone, 2-octanone, 4-hydroxy-4-methyl-2-pentanone and1-methyl-2-pyrrolidone, as such or in the form of a mixture, in anamount of 10 to 90% by weight, preferably in an amount of 15 to 85% byweight, based on the total amount of the medium.

In use, it has proven advantageous for the etching paste compositions,apart from the components mentioned hitherto, to comprise additivesselected from the group antifoams, thixotropic agents, flow-controlagents, deaerators, and adhesion promoters for improving the properties.Based on the total amount, 0 to 5% by weight of additives may be presentin the composition employed by the user.

An essential property of the compositions according to the invention istheir viscosity. The viscosity is generally usually defined as thematerial-dependent proportion of the frictional resistance whichcounters the movement when adjacent liquid layers are displaced.According to Newton, the shear resistance in a liquid layer between twosliding surfaces arranged parallel and moved relative to one another isproportional to the velocity or shear gradient G. The proportionalityfactor is a material constant which is known as the dynamic viscosityand has the dimension m Pa·s. In Newtonian liquids, the proportionalityfactor is pressure- and temperature-dependent. The degree of dependencehere is determined by the material composition. Liquids or substanceshaving an inhomogeneous composition have non-Newtonian properties. Theviscosity of these substances is additionally dependent on the sheargradient.

In industrial use, it has been found that the etching pastes accordingto the invention have particularly good properties if they have, owingto their overall composition, a viscosity at 20° C. in the range from 6to 35 Pa·s at a shear rate of 25 s⁻¹, preferably in the range from 10 to25 Pa·s at a shear rate of 25 s⁻¹ and especially at 15 to 20 Pa·s at ashear rate of 25 s⁻¹.

As already mentioned above, it has proven advantageous, in contrast toprevious knowledge, for inorganic and/or organic finely particulatepowders, which also contribute to thickening of the media, to be addedto the etching pastes according to the invention. WO 01/83391 A alsodescribes particle-free etching media for the etching of fine structuresand lines <100 μm in which homogeneously dispersed polymer serves forthe thickening. In the meantime, it has been found that the addition ofsuitable finely particulate inorganic and/or organic powders enablesparticularly thin lines to be printed and etched. Particularly suitablefor this purpose are polymer particles which interact with the othercomponents of the composition and form a network by means of chemicalbonds or a purely physical interaction at the molecular level. Therelative particle diameters of these systems can be in the range from 10nm to 30 μm. Corresponding polymer particles having a relative particlediameter in the range from 1 to 10 μm have proven particularlyadvantageous. Particles which are particularly suitable for the purposeaccording to the invention can consist of the following materials:

-   -   polystyrene    -   polyacrylate    -   polyamide    -   polyethylene    -   ethylene-vinyl acetate copolymer    -   ethylene-acrylic acid-acrylate terpolymer    -   ethylene-acrylate-maleic anhydride terpolymer    -   polypropylene    -   polyimide    -   polymethacrylate    -   melamine resin, urethane resin, benzoguanine resin, phenolic        resin    -   silicone resin    -   fluorinated polymers (PTFE, PVDF, . . . ), and    -   micronised waxes

The use of a very finely divided polyethylene powder, which is, forexample, currently marketed by DuPont PolymerPowders Switzerland underthe trade name COATHYLENE HX® 1681, having relative particle diametersd₅₀ value of 10 μm, has proven particularly suitable in the experiments.

These particulate thickeners can be added to the etching medium inamounts of 1 to 50% by weight, advantageously in the range from 10 to50% by weight, in particular from 25 to 35% by weight.

Also suitable in principle are particulate polymeric thickeners based on

-   -   polystyrene    -   polyacrylate    -   polyamide    -   polyimide    -   polymethacrylate    -   melamine resin, urethane resin, benzoguanine resin, phenolic        resin    -   silicone resin.

Etching media comprising inorganic, finely particulate powders selectedfrom the group carbon black and graphite are distinguished, inparticular, by significantly improved cleaning behaviour. After etchingat temperatures up to 500° C., in particular up to 390° C., but alsoafter doping at temperatures up to 1050° C., the residues of the etchingmedia can be rinsed off in a simple manner without the need forsubsequent rinsing since corresponding etching-paste residuesadvantageously detach from the surface in particulate form and can berinsed off simply without re-depositing again elsewhere.

Compared with the particle-free etching pastes described in WO 01/83391A, the addition of the particulate thickeners according to the inventionhas enabled the following improvements to be achieved:

-   I. The particulate thickening results in improved resilience of the    etching medium. The particles form a skeleton-like structure in the    etching medium. Similar structures are known to the person skilled    in the art from highly disperse silicic acid (for example Aerosil®).    In particular in screen or stencil printing of the etching pastes, a    broadening of the printed structures due to flow can be    substantially prevented or at least greatly restricted by the    present invention. The printed, and thus paste-covered, area    therefore corresponds substantially to the area specified in the    screen or stencil layout.    -   Many inorganic particles, such as, for example, silicic acid or        modified silicic acid, cannot be employed for thickening the        etching medium owing to their reactivity with the etching        component employed. For example, a chemical reaction of silicic        acid with NH₄HF₂ takes place if the latter serves as etching        component.-   II. With the aid of particulate thickening, lines of greater print    height with retained width are, in addition, printed on use of the    same screen or stencil than on use of corresponding particle-free    pastes, as described, for example, in WO 01/83391 A. This    simultaneously results in a greater application rate of etching    component per unit area. If relatively thick silicon dioxide or    silicon nitride layers (>100 nm) are to be etched, this is a    particular advantage for complete etching.-   III. The more pronounced non-Newtonian or thixotropic properties of    the novel etching pastes have a particularly advantageous effect for    screen or stencil printing and result in considerably improved    results. In particular, this is evident in a shortened etching time    or an increased etching rate for the same etching time and    especially in a greater etching depth in the case of relatively    thick layers.-   IV. The thickening associated with the addition of polymer particles    according to the invention results in a considerably lower binding    capacity of the etching paste. Given a specific choice of the    particles added, an increased etching rate and thus a considerably    increased etching depth are, surprisingly, achieved for the same    amount of added etching component.-   V. The significantly greater print height achieved under the same    printing conditions, i.e. on use of the same screen and the same    printing parameters, furthermore causes significantly delayed drying    of the printed etching species. This enables the etching species to    act on the substrate for longer. This is particularly important in    the case of accelerated etching under elevated temperatures. In    addition, the material remaining after the etching process can be    removed significantly more easily in the final cleaning process, in    particular since the paste residues detach from the surfaces in    finely divided form.

Significant improvements in the present compositions arise, inparticular, through considerably improved screen-printing behaviour,enabling continuous printing of surfaces to be treated withoutinterruptions. The use of the etching pastes according to the inventionenables considerably finer etching structures since the pastes havegreater viscosities on addition of the same amounts of thickener in thepresence of polymer particles. This enables the pastes to be applied inprinting with a higher paste layer and consequently the layers to beetched more deeply. The improved rinsing behaviour (wafer cleaning)after etching also shortens the time required for subsequent cleaning.In addition, the amount of solvent or water required for the rinsingoperation is reduced since residues of the etching media can be detachedfrom the treated surface after the etching operation by the finelyparticulate inorganic powders present thereon and rinsed off withoutleaving a residue.

For the preparation of the compositions according to the invention, thesolvents, etching components, thickeners, particles and additives aremixed successively with one another and stirred for a sufficient timeuntil a viscous paste having thixotropic properties has formed. Thestirring can be carried out with warming to a suitable temperature. Thecomponents are usually stirred with one another at room temperature.

Preferred uses of the printable etching pastes according to theinvention arise for the described processes for the structuring of oxidelayers applied to a support material, for the production of solar cellshaving a selective emitter layer on the light incidence side and for theproduction of solar cells having a selective emitter layer on the lightincidence side and a back-surface field on the back.

For application to the areas to be treated, the etching pastes can beprinted through a fine-mesh screen which contains the print stencil (oretched metal screens). In a further step, the pastes can be baked in thescreen-printing process by the thick-layer method (screen printing ofconductive metal pastes), enabling the electrical and mechanicalproperties to be fixed. On use of the etching pastes according to theinvention, the baking (firing through the dielectric layers) can insteadalso be omitted and the applied etching pastes washed off with asuitable solvent or solvent mixture after a certain exposure time. Theetching action is terminated by the washing-off.

Particularly suitable printing processes are essentially screen printingwith screen separation or stencil printing without separation. In screenprinting, the separation a of a screen is usually several hundred μmwith a tilt angle α between the edge of the squeegee, which pushes theetching printing paste over the screen, and the screen. The screen isheld by a screen frame, while the squeegee is passed over the screen ata squeegee velocity v and a squeegee pressure P. In the process, theetching paste is pushed over the screen. During this operation, thescreen comes into contact with the substrate in the form of a line overthe squeegee width. The contact between screen and substrate transfersthe vast majority of the screen printing paste located in the freescreen meshes onto the substrate. In the areas covered by the screenmeshes, no screen printing paste is transferred onto the substrate. Thisenables screen printing paste to be transferred in a targeted manneronto certain areas of the substrate.

After the end of the movement E, the squeegee is lifted off the screen.The screen is tensioned uniformly using a screen stretcher with ahydraulic/pneumatic tension and clamping device. The screen tension ismonitored by defined sag of the screen in a certain area at a certainweight using a dial gauge. With specific pneumatic/hydraulic printingmachines, the squeegee·pressure (P), the printing velocity (V), theoff-contact distance (a) and the squeegee path (horizontal and vertical,squeegee angle) can be set with various degrees of automation of theworking steps for trial and production runs.

Printing screens used here usually consist of plastic or steel-wirecloth. It is possible for the person skilled in the art to select clothshaving different wire diameters and mesh widths, depending on thedesired layer thickness and line width. These cloths are structureddirectly or indirectly using photosensitive materials (emulsion layer).For the printing of extremely fine lines and in the case of requisitehigh precision of successive prints, it may be advantageous to use metalstencils, which are likewise provided directly or indirectly with a holestructure or line structure.

In order to carry out the etching, an etching paste, as described, forexample, in Example 1, is prepared. Using an etching paste of this type,a thermal SiO₂ having a thickness of approx. 100 nm can be removed afterscreen printing. The etching is subsequently terminated by dipping theSi wafer into water and then rinsing with the aid of a fine water spray.

For the production of solar cells, wafers comprising p-doped Cz siliconhaving <100> orientation, for example, are selected. In these, a short,basic etching enables a structure to be produced on the surface whichimproves the light incidence geometry for reducing reflections. A thindopant coating film comprising a boron-containing compound can bespin-coated onto the back and dried. The wafers prepared in this way areplaced in a tray and introduced into an oven pre-heated to 1000 to 1100°C. An oxygen atmosphere is established in the oven, so that an oxidelayer forms directly on all wafer surfaces that are not covered by theboron dopant coating film. At the same time, boron is expelled from thedopant coating film and diffuses into the back of the wafers. p+-dopedregions with a depth of approx. 1 to 5 μm form. This embodiment of asolar cell is known to the person skilled in the art under the term“back-surface field”. The oxide layers formed on the front can now bestructured using the etching pastes described above.

For example, these oxide layers can be formed as masks for high n+phosphorus dopings for the formation of selective emitter layers, whilesignificantly less n+ doping is aimed at in the masked areas.

After opening of the pn junction, which would result in short circuitsin the solar cell, for example by plasma etching or opening using aLASER beam, the electrical contacts are applied to the front and back ofthe cell. This can be carried out by means of two successivescreen-printing steps using a paste, which may, besides the binders andoxidic additives, comprise conductive silver particles and/or aluminium.After the printing, the printed contacts are baked at about 700 to 800°C.

Compositions as described by this application are improved, printableetching pastes which can be employed extremely well for the etching ofsurfaces of glasses which comprise elements selected from the groupcalcium, sodium, aluminium, lead, lithium, magnesium, barium, potassium,boron, beryllium, phosphorus, gallium, arsenic, antimony, lanthanum,scandium, zinc, thorium, copper, chromium, manganese, iron, cobalt,nickel, molybdenum, vanadium, titanium, gold, platinum, palladium,silver, cerium, caesium, niobium, tantalum, zirconium, yttrium,neodymium and praseodymium.

In accordance with the invention, the novel etching pastes havingthixotropic, non-Newtonian properties are used to structure silicondioxide or nitride layers in a suitable manner during the process forthe production of products for photovoltaics, semiconductor technology,high-performance electronics, of solar cells or photodiodes. Etchingmedia having the composition described can in addition be employed inmineralogy or the glass industry and for the production of viewingwindows for valves or measuring instruments, of glass supports foroutdoor applications, for the production of etched glass surfaces in themedical, decorative and sanitary sectors, for the production of etchedglass containers for cosmetic articles, foods and beverages, for theproduction of markings or labels on containers and in flat-glassproduction, for the structuring of glasses for flat-panel screenapplications or for mineralogical, geological and microstructuralinvestigations.

For the etching and doping of the surfaces to be treated, thecompositions can be applied by screen, stencil, pad, stamp, ink-jet andmanual printing processes. These are processes having a high degree ofautomation and high throughput. Manual application of the etching mediaaccording to the invention is likewise possible.

Owing to the particular physical properties, both at room temperatureand also at elevated temperatures, the novel etching media are suitablefor extremely demanding applications and can be employed for theproduction of glass supports for solar cells or for heat collectors.They can be used for the etching of SiO₂— or silicon nitride-containingglasses as uniform homogeneous non-porous and porous solids or ofcorresponding non-porous and porous glass layers of variable thicknesswhich have been produced on other substrates. In this connection, theseetching media are particularly suitable for the removal of siliconoxide/doped silicon oxide and silicon nitride layers, for the selectiveopening of passivation layers of silicon oxide and silicon nitride forthe production of two-stage selective emitters and/or local p⁺back-surface fields in the process for the production of semiconductorcomponents and integrated circuits thereof or of components forhigh-performance electronics. In these applications, the etching mediumis applied over the entire area or selectively in a suitable manner in asingle process step to the semiconductor surface to be etched, ifnecessary activated by input of energy, and removed again after anexposure time of 10 s-15 min, preferably after 30 s to 2 min. Theetching can be carried out at elevated temperatures in the range from 30to 500° C., preferably in the range from 200 to 450° C. The etching withthe novel etching media according to the invention is very particularlypreferably carried out in a temperature range from 320 to 390° C.

The media according to the invention can be applied over the entire areain a simple manner by methods known to the person skilled in the art.The novel media can also be applied selectively using an etch mask onlyto the areas where etching is desired. When etching of the entire areaor in selectively printed areas is complete, doping can be carried outby further heating or the spent etching medium is rinsed off using asolvent or solvent mixture or burnt off by heating. The etching mediumis preferably rinsed off with water when etching is complete.

The paste is usually printed onto the surface to be etched in a singleprocess step and removed again after a pre-specified exposure time atsuitable temperature. In this way, the surface is etched and structuredin the printed areas, while unprinted areas are retained in the originalstate.

In this way, all masking and lithography steps otherwise necessary aresuperfluous. The etching operation can be carried out with or withoutinput of energy, for example in the form of thermal radiation or with IRradiation.

The actual etching process is subsequently terminated by washing thesurfaces with water and/or a suitable solvent. More precisely, theresidues of the particle-containing etching media are rinsed off theetched and optionally doped surfaces using a suitable solvent whenetching is complete.

The surface to be etched can, as already stated, be a surface orpart-surface of silicon oxide- or silicon nitride-based glass and othersilicon oxide- and silicon nitride-based systems, and/or a surface orpart-surface of a porous and non-porous layer of glass and other siliconoxide- and silicon nitride-based systems on a support material.

During the application, the novel etching pastes described exhibitparticularly advantageous properties compared with known compositions.In particular with respect to the surface cleaning following the etchingoperation, the novel formulations have more optimum properties. Theimproved properties become particularly clear on use of correspondingetching media in paste form.

It has been found that the pastes prepared exhibit improved properties,in particular, through the addition of finely particulate, inorganicpowders (graphite and/or carbon black) and/or finely particulate organicpowders (plastic powders), more precisely during printing, but alsoduring and after the etching of SiN_(x) or SiO₂ layers at temperaturesbetween 320 and 400° C. An essential advantage of the novel etchingmedia or paste formulations consists, in particular, in that the addedinorganic powders do not melt at the high temperatures during theetching at 320-400° C. The active etching medium consequently onlyreacts in the desired areas. The novel etching media prove to beparticularly advantageous during the cleaning of the etched andoptionally doped surfaces. This is usually carried out usinghigh-purity, deionised water (bidistilled water) in an ultrasound bath.

After the etching operation, the paste residues do not, like knownetching pastes, detach from the treated surface in strips duringcleaning, but instead decompose and are taken up in the cleaning wateras fine particles. This advantage is found in particular for pastes towhich at least one inorganic powder having a relative particle size <5μm has been added.

Furthermore, the use of a salt-like additive (fluxing agent additive) inthe etching paste enables significantly improved cleaning to beachieved. For this purpose, a fluxing agent additive which has a meltingpoint <300° C. and a decomposition point >400° C. and which at the sametime has very good water solubility is added to the paste. After theetching step at 320-390° C., the cooled paste residue can be detachedsignificantly better during the subsequent rinsing operation.

Suitable fluxing agent additives have proven to be compounds selectedfrom the group dimethylammonium chloride, diammonium hydrogen-phosphate,diethylamine phosphate, urea, magnesium stearate, sodium acetate,triethanolamine hydrochloride and oxalic acid dihydrate. For thispurpose, they can be added to the etching media individually or in theform of a mixture. In accordance with the invention, these fluxing agentadditives may be present in the etching media in an amount of 0.05 to25% by weight, based on the total amount. Media in which one or morefluxing agent additives are present in an amount of up to 17% by weighthave particularly good properties in use.

These improved properties give rise to significant advantages for use ofthe etching media according to the invention in the mass production ofsolar cells compared with the use of conventional etching pastes sincethe paste residues can be removed in a simple manner in the cleaningstep following the etching and detached paste residues do not remain onthe surfaces to be treated and do not re-deposit from the cleaningwater. This means that the cleaning operation can be optimised and therequisite amount of high-purity distilled water can be reduced.

Overall, the use of the compositions according to the invention foretching in the form of pastes thus enables large numbers of pieces to beetched and optionally doped inexpensively in a suitable automatedprocess on an industrial scale.

For better understanding and for illustration, examples are given belowwhich are within the scope of protection of the present invention, butare not suitable for restricting the invention to these examples. Theseexamples also serve for the illustration of possible variants.

It goes without saying that, both in the examples given and also in theremainder of the description, the quoted percentage data of thecomponents present in the compositions always add up to a total of 100%and not more.

EXAMPLES Example 1

Etching paste consisting of a particulate thickener

465 g of phosphoric acid (85%)are added with stirring to a solvent mixture consisting of218 g of deionised water223 g of 1-methyl-2-pyrrolidone1.6 g of ethylene glycol33 g of dimethylammonium chloride.

The mixture is subsequently stirred vigorously.

100 g of Vestosint 2070

are then added to the clear homogeneous mixture, which is stirred for afurther 2 hours.

The paste, which is now ready to use, can be printed using a 280 meshstainless-steel cloth screen. In principle, polyester or similar screenmaterials can also be used.

The etching paste prepared has proven to be stable on storage over along period with retention of the advantageous etching properties.

Further examples of compositions according to the invention havingadvantageous properties are given in the annexed tables.

TABLE Triethylene glycol Lactic Diammonium Dimethyl- monomethylStabileze Polyethylene PVP Natrosol Vestosint acid H₃PO₄ 1-Methyl-Ceridust Carbon Ethylene Aerosil PVP hydrogen- Diethylamine ammoniumether H₂O QM glycol K90 GR250 PA 2070 (90%) (85%) 2-pyrrolidone 9202 Fblack Graphite glycol 200 K30 phosphate phosphate chloride Batch [g] [g][g] [g] [g] [g] [g] [g] [g] [g] [g] [g] [g] [g] [g] [g] [g] [g] [g] 1 0218 8 0 0 8 0 0 465 223 275 19 0 1.6 0 0 0 0 33 2 0 219 7.7 0 0 8.5 0 0463 223 276 17 0 2 0 0 0 0 35 3 0 220 7.4 0 0 9 0 0 461 223 277 15 0 2.40 0 0 0 37 4 0 221 7.1 0 0 9.5 0 0 459 223 278 13 0 2.8 0 0 0 0 39 5 0222 6.8 0 0 10 0 0 457 223 279 11 0 3.2 0 0 0 0 41 6 0 223 6.5 0 0 10.50 0 455 223 280 9 0 3.6 0 0 0 0 43 7 0 224 6.2 0 0 11 0 0 453 223 281 70 3 0 0 0 0 34 8 0 225 5.9 0 0 11.5 0 0 451 223 282 8 0 2.4 0 0 0 0 25 90 226 5.6 0 0 12 0 0 449 223 283 9 0 1.8 0 0 0 0 16 10 0 227 5.3 0 012.5 0 0 447 223 284 10 0 1.2 0 0 0 0 17 11 0 228 5 0 0 13 0 0 445 223285 11 0 0.6 0 0 0 0 18 12 0 229 4.7 0 0 13.5 0 0 443 223 286 12 0 0 0 00 0 19 13 0 0 0 0 0 0 0 0 450 466 302 13 0 0 0 60 0 0 76 14 0 0 0 0 0 00 0 452 464 291 19 0 0 0 59.5 0 0 100 15 0 0 0 0 0 0 0 0 454 462 280 250 0 0 59 0 0 124 16 0 0 0 0 0 0 0 0 456 460 269 31 0 0 0 58.5 0 0 123 170 0 0 0 0 0 0 0 458 458 258 37 0 0 0 58 0 0 122 18 0 0 0 0 0 0 0 0 460456 247 43 0 0 0 57.5 0 0 121 19 0 0 0 0 0 0 0 0 462 454 236 49 0 0 0 570 0 120 20 0 0 0 0 0 0 0 0 464 452 225 55 0 0 0 56.5 0 0 119 21 0 0 0 00 0 0 0 450 466 214 61 0 0 0 60 0 0 118 22 0 0 0 0 0 0 0 0 452 464 20367 0 0 0 59.5 0 0 119 23 0 0 0 0 0 0 0 0 454 462 192 73 0 0 0 59 0 0 12024 0 0 0 0 0 0 0 0 456 460 181 79 0 0 0 58.5 0 0 121 25 0 0 0 0 0 0 0 0458 458 170 85 0 0 0 58 0 0 122 26 0 0 0 0 0 0 0 0 460 456 252 68 0 0 057.5 0 0 130 27 0 0 0 0 0 0 0 0 462 454 249 51 0 0 0 57 0 0 138 28 0 0 00 0 0 0 0 464 452 246 50 0 0 0 56.5 0 0 146 29 1 0 0 0 0 0 0 0 466 450243 49 0 0 0 56 0 0 154 30 2 0 0 0 0 0 0 0 468 448 240 48 0 0 0 55.5 0 0162 31 2 0 0 0 0 0 0 0 470 446 237 47 0 0 0 55 0 0 170 32 0 218 8 0 0 80 0 465 223 275 0 19 1.6 0 0 0 33 0 33 0 219 7.7 0 0 8.5 0 0 463 223 2760 17 2 0 0 0 35 0 34 0 220 7.4 0 0 9 0 0 461 223 277 0 15 2.4 0 0 0 37 035 0 221 7.1 0 0 9.5 0 0 459 223 278 0 13 2.8 0 0 0 39 0 36 0 222 6.8 00 10 0 0 457 223 279 0 11 3.2 0 0 0 41 0 37 0 223 6.5 0 0 10.5 0 0 455223 280 0 9 3.6 0 0 0 43 0 38 0 224 6.2 0 0 11 0 0 453 223 281 0 7 3 0 00 34 0 39 0 225 5.9 0 0 11.5 0 0 451 223 282 0 8 2.4 0 0 0 25 0 40 0 2265.6 0 0 12 0 0 449 223 283 0 9 1.8 0 0 0 16 0 41 0 227 5.3 0 0 11.5 0 0447 223 284 0 10 1.2 0 0 0 17 0 42 0 228 5 0 0 13 0 0 445 223 285 0 110.6 0 0 0 18 0 43 0 229 4.7 0 0 13.5 0 0 443 223 286 0 12 0 0 0 0 19 044 0 0 0 0 0 0 0 0 450 466 302 0 13 0 0 60 0 76 0 45 0 0 0 0 0 0 0 0 452464 291 0 19 0 0 59.5 0 100 0 46 0 0 0 0 0 0 0 0 454 462 280 0 25 0 0 590 124 0 41 0 0 0 0 0 0 0 0 456 460 269 0 31 0 0 58.5 0 123 0 48 0 0 0 00 0 0 0 458 458 258 0 37 0 0 58 0 122 0 49 0 0 0 0 0 0 0 0 460 456 247 043 0 0 57.5 0 121 0 50 0 0 0 0 0 0 0 0 462 454 236 0 49 0 0 57 0 120 051 0 0 0 0 0 0 0 0 464 452 225 0 55 0 0 56.5 0 119 0 52 0 0 0 0 0 0 0 0450 466 214 0 61 0 0 60 0 118 0 53 0 0 0 0 0 0 0 0 452 464 203 0 61 0 059.5 0 119 0 54 0 0 0 0 0 0 0 0 454 462 192 0 73 0 0 59 0 120 0 55 0 0 00 0 0 0 0 456 460 181 0 19 0 0 58.5 0 121 0 56 0 0 0 0 0 0 0 0 458 458170 0 85 0 0 58 0 122 0 57 0 0 0 0 0 0 0 0 460 456 252 0 68 0 0 57.5 0130 0 58 0 0 0 0 0 0 0 0 462 454 249 0 51 0 0 57 0 138 0 59 0 0 0 0 0 00 0 464 452 246 0 50 0 0 56.5 0 146 0 60 1 0 0 0 0 0 0 0 466 450 243 049 0 0 56 0 154 0 61 2 0 0 0 0 0 0 0 468 448 240 0 48 0 0 55.5 0 162 062 2 0 0 0 0 0 0 0 470 446 237 0 47 0 0 55 0 170 0 63 0 218 8 0 0 8 0 0465 223 275 0 0 1.6 19 0 33 0 0 64 0 219 7.7 0 0 8.5 0 0 463 223 276 0 02 17 0 35 0 0 65 0 220 7.4 0 0 9 0 0 461 223 277 0 0 2.4 15 0 37 0 0 660 221 7.1 0 0 9.5 0 0 459 223 278 0 0 2.8 13 0 39 0 0 67 0 222 6.8 0 010 0 0 457 223 279 0 0 3.2 11 0 41 0 0 68 0 223 6.5 0 0 10.5 0 0 455 223280 0 0 3.6 9 0 43 0 0 69 0 224 6.2 0 0 11 0 0 453 223 281 0 0 3 7 0 340 0 70 0 225 5.9 0 0 11.5 0 0 451 223 232 0 0 2.4 8 0 25 0 0 71 0 2265.6 0 0 12 0 0 449 223 283 0 0 1.8 9 0 16 0 0 72 0 227 5.3 0 0 12.5 0 0447 223 284 0 0 1.2 10 0 17 0 0 73 0 228 5 0 0 13 0 0 445 223 285 0 00.6 11 0 18 0 0 74 0 229 4.7 0 0 13.5 0 0 443 223 286 0 0 0 12 0 19 0 075 0 0 0 0 0 0 0 0 450 466 302 0 0 0 13 60 76 0 0 76 0 0 0 0 0 0 0 0 452464 291 0 0 0 19 59.5 100 0 0 77 0 0 0 0 0 0 0 0 454 462 280 0 0 0 25 59124 0 0 78 0 0 0 0 0 0 0 0 456 460 269 0 0 0 31 58.5 123 0 0 79 0 0 0 00 0 0 0 458 458 258 0 0 0 37 58 122 0 0 80 0 0 0 0 0 0 0 0 460 456 247 00 0 43 57.5 121 0 0 81 0 0 0 0 0 0 0 0 462 454 236 0 0 0 49 57 120 0 082 0 0 0 0 0 0 0 0 464 452 225 0 0 0 55 56.5 119 0 0 83 0 0 0 0 0 0 0 0450 466 214 0 0 0 61 60 118 0 0 84 0 0 0 0 0 0 0 0 452 464 203 0 0 0 6759.5 119 0 0 85 0 0 0 0 0 0 0 0 454 462 192 0 0 0 73 59 120 0 0 86 0 0 00 0 0 0 0 456 460 181 0 0 0 79 58.5 121 0 0 87 0 0 0 0 0 0 0 0 458 458170 0 0 0 85 58 122 0 0 88 0 0 0 0 0 0 0 0 460 456 252 0 0 0 68 57.5 1300 0 89 0 0 0 0 0 0 0 0 462 454 249 0 0 0 51 57 138 0 0 90 0 0 0 0 0 0 00 464 452 246 0 0 0 50 56.5 146 0 0 91 1 0 0 0 0 0 0 0 466 450 243 0 0 049 56 154 0 0 92 2 0 0 0 0 0 0 0 468 448 240 0 0 0 48 55.5 162 0 0 93 20 0 0 0 0 0 470 446 237 0 0 0 47 55 170 0 0

1.-30. (canceled)
 31. A composition for the etching and optionallydoping of a silicon oxide, silicon nitride or glass layer comprising: atleast one etching component comprising: one or more forms of phosphoricacid, a phosphoric acid salt or a compound which decomposes to thecorresponding phosphoric acid, or at least one of hydrochloric acid,sulfuric acid or nitric acid; optionally, at least one organic acidselected from the group of alkylcarboxylic acids, hydroxycarboxylicacids and dicarboxylic acids; at least one solvent; a finely particulateinorganic powder of graphite and/or carbon black having a relativeparticle diameter of less than 5 μm; a finely particulate organic powderin the form of a finely particulate plastic powder having a relativeparticle diameter in the range from 10 nm to 50 μm selected from thegroup of polystyrenes, polyacrylates, polyamides, polyimides,polymethacrylates, melamine resin, urethane resin, benzoguanine resin,phenolic resin, silicone resins, micronised cellulose, fluorinatedpolymers (PTFE, PVDF) and micronised waxes; optionally, a finelyparticulate inorganic powder selected from the group of aluminum oxide,calcium fluoride, boron oxide, and sodium chloride; at least one fluxingagent additive; optionally a homogeneously dissolved organic thickener;and optionally, one or more antifoam, thixotropic agent, flow-controlagent, deaerator or adhesion promoter additives; in the form of aprintable paste.
 32. The composition of claim 31, wherein said printablecomposition in the form of a paste comprises said finely particulateplastic powder have a relative particle diameter in the range from 10 nmto 50 μm.
 33. The composition of claim 31, wherein said printablecomposition in the form of a paste comprises said finely particulateplastic powder have a relative particle diameter in the range from 100nm to 30 μm.
 34. The composition of claim 31, wherein said printablecomposition in the form of a paste comprises said finely particulateplastic powder have a relative particle diameter in the range from 1 μmto 10 μm.
 35. The composition of claim 31, wherein the compositioncomprises the inorganic and organic powders in an amount of 1 to 80% byweight, based on the total amount of the composition.
 36. Thecomposition of claim 31, wherein the composition comprises the inorganicand organic powders in an amount of 10 to 50% by weight, based on thetotal amount of the composition.
 37. The composition of claim 31,wherein the composition comprises the inorganic and organic powders inan amount of 20 to 40% by weight, based on the total amount of thecomposition.
 38. The composition of claim 31, wherein the compositioncomprises the at least one etching component in an amount of 12 to 30%by weight, based on the total amount of the composition.
 39. Thecomposition of claim 31, wherein the composition comprises the at leastone etching component in an amount of 2 to 20% by weight, based on thetotal amount of the composition.
 40. The composition of claim 31,wherein the composition comprises the at least one etching component inan amount of 5 to 15% by weight, based on the total amount of thecomposition.
 41. The composition of claim 31, wherein the compositioncomprises thickeners in an amount of 3 to 20% by weight, based on thetotal amount of the composition.
 42. The composition of claim 31,wherein the composition further comprises an organic acid selected fromthe group consisting of formic acid, acetic acid, lactic acid and oxalicacid.
 43. The composition of claim 31, wherein the acids are in aconcentration range from 0 to 80% by weight, based on the total amountof the composition, where the acids each have a pKa value of between 0and
 5. 44. The composition of claim 31, wherein the solvent comprises:water, mono- or polyhydric alcohols or ethers thereof, esters, esters ofcarbonic acid, ketones, or mixtures thereof, in an amount of 10 to 90%by weight, based on the total amount of the composition.
 45. Thecomposition of claim 44, wherein the solvent comprises water, glycerol,1,2-propanediol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol,2-ethyl-1-hexenol, ethylene glycol, diethylene glycol, dipropyleneglycol, ethylene glycol monobutyl ether, triethylene glycol monomethylether, diethylene glycol monobutyl ether, dipropylene glycol monomethylether, [2,2-butoxy(ethoxy)]ethyl acetate, propylene carbonate,acetophenone, methyl-2-hexanone, 2-octanone,4-hydroxy-4-methyl-2-pentanone, 1-methyl-2-pyrrolidone or mixturesthereof.
 46. The composition of claim 31, wherein the compositioncomprises one or more homogeneously dissolved thickeners selected fromthe group consisting of: cellulose and cellulose derivatives, starch andstarch derivatives, polyvinylpyrrolidone, and polymers based onacrylates or functionalised vinyl units, in an amount of 0.5 to 25% byweight, based on the total amount of the composition.
 47. Thecomposition of claim 31, wherein the composition comprises 0 to 5% byweight, based on the total amount of the composition, of additivesselected from antifoams, thixotropic agents, flow-control agents,deaerators, and adhesion promoters.
 48. The composition of claim 31,wherein the composition has a viscosity at 20° C. in the range from 6 to35 Pa·s at a shear rate of 25 s⁻¹.
 49. The composition of claim 31,wherein the composition has a viscosity at 20° C. in the range from 10to 25 Pa·s at a shear rate of 25 s⁻¹.
 50. The composition of claim 31,wherein the composition has a viscosity at 20° C. in the range from 15to 20 Pa·s at a shear rate of 25 s⁻¹.
 51. The composition of claim 31,wherein the composition comprises fluxing agent additives selected fromthe group consisting of dimethylammonium chloride, diammoniumhydrogenphosphate, diethylamine phosphate, urea, magnesium stearate,sodium acetate, triethanolamine hydrochloride and oxalic acid dihydrate,individually or in the form of a mixture, in an amount of 0.05 to 25% byweight, based on the total amount of the composition.